U.S. patent number 9,125,748 [Application Number 14/300,984] was granted by the patent office on 2015-09-08 for method and implant for replacing damaged meniscal tissue.
This patent grant is currently assigned to DEPUY SYNTHES PRODUCTS, INC.. The grantee listed for this patent is DEPUY SYNTHES PRODUCTS, LLC. Invention is credited to Nicolas Bouduban, Philippe Gedet, Beat Lechmann.
United States Patent |
9,125,748 |
Gedet , et al. |
September 8, 2015 |
Method and implant for replacing damaged meniscal tissue
Abstract
A method and apparatus for replacing damaged meniscal tissue
includes a meniscus implant including a porous body having a
plurality of interconnected open micro-pores and one or more open
cavities for receiving meniscal tissue. The interconnected
micro-pores are arranged to allow fluid to flow into the porous
body and are in fluid communication with the one or more open
cavities.
Inventors: |
Gedet; Philippe (Oberdorf,
CH), Lechmann; Beat (Oberdorf, CH),
Bouduban; Nicolas (Oberdorf, CH) |
Applicant: |
Name |
City |
State |
Country |
Type |
DEPUY SYNTHES PRODUCTS, LLC |
Raynham |
MA |
US |
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Assignee: |
DEPUY SYNTHES PRODUCTS, INC.
(Raynham, MA)
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Family
ID: |
45755585 |
Appl.
No.: |
14/300,984 |
Filed: |
June 10, 2014 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20140296980 A1 |
Oct 2, 2014 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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13397482 |
Feb 15, 2012 |
8771353 |
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61450517 |
Mar 8, 2011 |
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61472913 |
Apr 7, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F
2/3872 (20130101); A61F 2/30756 (20130101); A61F
2002/30586 (20130101); A61F 2002/3068 (20130101); A61L
2430/06 (20130101); A61F 2002/30733 (20130101); A61F
2310/00365 (20130101); A61F 2002/3092 (20130101); A61F
2230/0013 (20130101); A61F 2002/30581 (20130101); A61F
2002/30841 (20130101); A61F 2002/30766 (20130101); A61F
2002/30761 (20130101) |
Current International
Class: |
A61F
2/08 (20060101); A61F 2/38 (20060101); A61F
2/30 (20060101) |
Field of
Search: |
;623/14.12 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 053 460 |
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Jun 1982 |
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EP |
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2 272 467 |
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Jan 2011 |
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EP |
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2 635 678 |
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Mar 1990 |
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FR |
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2004/075940 |
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Sep 2004 |
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WO |
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2005/122966 |
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Dec 2005 |
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WO |
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2007/084878 |
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Jul 2007 |
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WO |
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Other References
International Search Report and Written Opinion (PCT/US2012/025417)
Apr. 24, 2012. cited by applicant.
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Primary Examiner: Willse; David H
Assistant Examiner: Blanco; Javier
Attorney, Agent or Firm: Dunlap Codding, P.C.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a divisional of U.S. Ser. No. 13/397,482, filed
Feb. 15, 2012, now U.S. Pat. No. 8,771,353, which claims priority
to U.S. Provisional Application Ser. No. 61/450,517, filed on Mar.
8, 2011, and to U.S. Provisional Application Ser. No. 61/472,913,
filed on Apr. 7, 2011, the entire contents of each being hereby
expressly incorporated herein by reference.
Claims
What is claimed is:
1. A method for replacing damaged meniscal tissue, comprising:
performing an incision permitting a surgical access to at least one
of the menisci in a knee joint; cutting away a portion of a native
meniscus so that a rim of native meniscus material at the outer
side of the native meniscus remains; obtaining a meniscus implant
including a porous body having a plurality of open cavities spaced
along the porous body for receiving native meniscus material and a
plurality of interconnected open micro-pores in fluid communication
with the open cavities; obtaining one or more pieces of a native
meniscus, wherein the pieces are punched out of the cut away
portion of the patient's native meniscus; inserting the pieces of
native meniscus into the cavities in the meniscus implant;
inserting the meniscus implant between a respective femoral condyle
and the tibial plateau in a patient's knee joint so that an outer
convex peripheral surface of the porous body abuts an inner concave
side of the rim of remaining native meniscus material; fixing the
meniscus implant to the rim of native meniscus material; and
closing the incision.
2. The method of claim 1, wherein the pieces of native meniscus are
cylindrical or prismatic.
3. The method of claim 1, wherein the cavities of the meniscus
implant have a diameter d, and wherein the step of obtaining one or
more pieces of native meniscus further comprises: punching out the
native meniscus to have a diameter D greater than the diameter d of
the cavities of the meniscus implant.
4. The method of claim 1 wherein the cavities of the meniscus
implant penetrate through the porous body from an upper surface to
a lower surface of the porous body and wherein the porous body
further comprises transverse passages penetrating through the
porous body and through the cavities from the outer convex
peripheral surface to an inner concave peripheral surface.
5. The method of claim 4 further comprising the step of: fixing the
pieces of native meniscus within the cavities of the porous body by
leading a suture through the transverse passages, through the
pieces of native meniscus, and through the rim of native
meniscus.
6. The method of claim 5, wherein the suture is led through the
transverse passages and through the pieces of native meniscus in a
meandering path.
7. The method of claim 1, wherein the cavities of the meniscus
implant penetrate into the porous body from the outer convex
peripheral surface.
8. The method of claim 1, further comprising the step of: fixing
the pieces of native meniscus within the cavities of the porous
body by gluing the pieces into the cavities.
9. The method of claim 8, further comprising the step of: fixing
the pieces of native meniscus within the cavities of the porous
body by gluing a grid or a membrane on the outer convex peripheral
surface over each cavity.
10. The method of claim 1 further comprising the steps of: drilling
a bore hole from a side surface of the tibia through the tibial
plateau at the former attachment site of a horn of the native
meniscus; and fixing a horn of the meniscus implant to the tibia
with a suture led through the bore hole.
11. The method of claim 1, wherein the interconnected pores of the
porous body are filled with a hydrogel-like substance containing
cells.
12. A method for replacing damaged meniscal tissue, comprising:
performing an incision permitting a surgical access to at least one
of the menisci in a knee joint; cutting away a portion of a native
meniscus so that a rim of native meniscus material at the outer
side of the native meniscus remains; obtaining a meniscus implant
including a substantially C-shaped porous body comprising an outer
convex peripheral surface, an inner concave peripheral surface, an
upper surface, a lower surface, and a cross-sectional area in a
plane orthogonal to the lower surface which tapers from the outer
convex peripheral surface to the inner concave peripheral surface,
the porous body having a plurality of open cavities spaced along
the porous body for receiving native meniscus material and a
plurality of interconnected open micro-pores in fluid communication
with the open cavities; obtaining one or more pieces of a native
meniscus, wherein the pieces are punched out of the cut away
portion of the patient's native meniscus; inserting the pieces of
native meniscus into the cavities in the meniscus implant;
inserting the meniscus implant between a respective femoral condyle
and the tibial plateau in a patient's knee joint so that the outer
convex peripheral surface of the porous body abuts an inner concave
side of the rim of remaining native meniscus material; fixing the
meniscus implant to the rim of native meniscus material; and
closing the incision.
13. The method of claim 12, wherein the cavities of the meniscus
implant have a diameter d, and wherein the step of obtaining one or
more pieces of native meniscus further comprises: punching out the
native meniscus to have a diameter D greater than the diameter d of
the cavities of the meniscus implant.
14. The method of claim 12 wherein the cavities of the meniscus
implant penetrate through the porous body from the upper surface to
the lower surface of the porous body and wherein the porous body
further comprises transverse passages penetrating through the
porous body and through the cavities from the outer convex
peripheral surface to the inner concave peripheral surface.
15. The method of claim 14 further comprising the step of: fixing
the pieces of native meniscus within the cavities of the porous
body by leading a suture through the transverse passages, through
the pieces of native meniscus, and through the rim of native
meniscus.
Description
BACKGROUND
1. Field of the Inventive Concepts
The inventive concepts disclosed herein generally relate to medical
implants, and more particularly but not by way of limitation to a
meniscus implant for replacing damaged meniscal tissue and to a
method for using thereof.
2. Brief Description of Related Art
The menisci are responsible for shock absorption, load
transmission, lubrication, and stability of the knee joint. The
menisci are important in reducing the incidence of degenerative
joint disease. Unfortunately, after trauma or a severe injury the
meniscus may be damaged, such as by fissures forming in the
meniscus, for example. Damage to the meniscus is associated with
changes in joint function that can lead to disability and
degenerative joint changes. One of the strategies for meniscal
repair suggests the use of biocompatible synthetic or natural
scaffolds as a substrate to promote remodeling and healing of the
defect. In case of too many fissures, the meniscus may have to be
trimmed in a way that only an outer rim of meniscus may be left. A
meniscus implant made of a synthetic or natural material may be
anchored to the rim via surgical sutures, for example.
The discussion about meniscal repair has been characterized by the
debate of meniscectomy (i.e., partial or complete removal of the
native meniscus) versus meniscal repair. It has been shown that
meniscectomy increases the risk of developing osteoarthritis of the
knee joint. Whenever possible, native meniscus tissue should be
preserved by surgically sewing and reshaping it to avoid loss of
joint stability and the concentration of mechanical forces on the
articular cartilage of the femoral condyle and the tibia plateau.
In cases where a meniscectomy is inevitable, two different types of
meniscus implants are available on the market. One is a
fully-synthetic solution and the other is a natural solution based
for example on purified Type-I collagen fibers. The synthetic and
the natural solution are scaffolds with a porous structure to
promote tissue ingrowth. Both concepts are based on the anchorage
to the rim and to the posterior and anterior horn of the meniscus
with sutures or a dowel-like device.
An example on the market in the category of natural solutions is
Menaflex.TM., formerly CMI, from ReGen Biologics (ReGen Biologics
Inc., 411 Hackensack Avenue, Hackensack, N.J. 07601, USA). The
Menaflex.TM. collagen The meniscus implant is a resorbable
collagen-based surgical mesh composed primarily of Type-I collagen.
It serves to reinforce damaged or weakened meniscus tissue and
provides a resorbable scaffold for replacement by the patient's own
tissue. Menaflex.TM. is intended for use in patients with an
irreparable meniscus tear, or loss of meniscus tissue. An example
in the category of synthetic implant is Actifit.TM. from Orteq
Bioengineering (Orteq Ltd, 10 Greycoat Place, London, SW1P 1SB,
United Kingdom). Actifit.TM. is a resilient, flexible, highly
porous, and biocompatible synthetic scaffold. Its structure
comprises open continuous pores, through which blood vessels can
rapidly grow into the implant. The blood transports cells and
nutrients that initiate the growth of new meniscus-like tissue
inside the synthetic scaffold.
BRIEF SUMMARY OF THE INVENTIVE CONCEPTS
In one embodiment, the present disclosure relates to a method for
replacing damaged meniscal tissue using a meniscus implant
including a porous body with interconnected open micro-pores and
one or more open cavities for receiving native meniscus material.
More specifically, one method comprises the steps of:
A) performing an incision permitting a surgical access to at least
one of the menisci in a knee joint;
B) cutting away a portion of a native meniscus so that a rim of
native meniscus material at the outer convex side of the native
meniscus remains;
C) selecting a meniscus implant of a desired size and having one or
more open cavities;
D) obtaining one or more pieces of the native meniscus;
E) inserting the pieces into the cavities of the meniscus
implant;
F) inserting the meniscus implant including the pieces between a
respective femoral condyle and the tibial plateau in a patient's
knee joint so that the outer convex peripheral surface of the
porous body abuts the inner concave side of the rim of remaining
native meniscus material; G) fixing the meniscus implant to the rim
of native meniscus material; and H) closing the incision.
The meniscus implant may be fixed to the rim of native meniscus
material with a plurality of suture loops. Alternatively, the
meniscus implant can be fixed to the rim of native meniscus
material by a dowel like device.
The concept of this meniscus implant, which can be made of a porous
synthetic material, is based on empty spaces or cavities which can
be filled with native meniscus material that was recuperated during
the trimming procedure.
In one embodiment of the method, the porous body may be C-shaped
and comprise between about 1 and about 10 open cavities.
In another embodiment of the method, the pieces of native meniscus
are punched out of the cut away portion of the patient's native
meniscus. Alternatively, native meniscus material from a donor can
be used.
In another embodiment of the method, the pieces of meniscus are
cylindrical or prismatical.
In yet another embodiment, the method further comprises before step
D) the substep of:
trimming the meniscus implant to a desired shape.
By this means the advantage can be achieved that the meniscus
implant can have a pre-operative shape of a complete meniscus, so
that the same meniscus implant could be used in the case of a total
meniscectomy as well. However, in most cases the native meniscus is
only partly cut away so that a meniscal rim is maintained.
In a further embodiment of the method:
under step C) a meniscus implant is selected where the cavities of
the porous body have a diameter d; and
under step D) a punching die is used that has a bore with a
diameter D.sub.i that is greater than d so that the pieces that are
punched out of the cut away native meniscus material can be fixed
in the cavities by a press fit.
In a further embodiment of the method under step C) a meniscus
implant is selected where the cavities penetrate through the porous
body from the upper surface to the lower surface of the porous body
and wherein the porous body further comprises transverse passages
penetrating through the porous body and through the cavities from
the outer convex peripheral surface to the inner concave peripheral
surface.
In a further embodiment, the method further comprises before step
F) the substep of:
fixing the pieces of meniscus within the cavities of the porous
body by leading a suture through the transverse passages and
through the pieces, preferably in the middle of the height of the
pieces.
In a still further embodiment of the method, the suture is
subsequently led through the transverse passages and through the
pieces in a meander line. Therewith, the advantage can be achieved
that the suture can be firmly tightened and two knots at the ends
of the suture only are necessary.
In yet a further embodiment of the method under step C) a meniscus
implant is selected where the cavities penetrate into the porous
body from the outer convex peripheral surface in the form of pocket
holes.
In another embodiment, the method further comprises before step F)
the substep of:
fixing the pieces of meniscus within the cavities of the porous
body by gluing the pieces into the cavities.
In an alternative embodiment the method further comprises before
step F) the substep of:
fixing the pieces within the cavities of the porous body by gluing
a grid or a membrane on the outer convex peripheral surface over
each cavity.
In again another embodiment of the method step G) further comprises
the substeps of:
drilling a bore hole from a side surface of the tibia through the
tibial plateau at the former attachment site of a horn of the
native meniscus; and
fixing a horn of the meniscus implant to the tibia with a thread
lead through the bore hole or with a stopper attached to a horn of
the meniscus implant and pressed into the bore hole.
In yet another embodiment of the method, the interconnected pores
of the porous body are filled with a hydrogel-like substance
containing cells.
According to a further aspect of the present disclosure, there is
provided a meniscus implant for replacing damaged meniscal tissue
including a porous body with a central axis; the porous body
comprising: a) an outer convex peripheral surface and an inner
concave peripheral surface; b) an upper surface and a lower
surface; and c) a cross-sectional area orthogonal to the central
axis and tapering towards the inner concave peripheral surface,
wherein d) the porous body comprises interconnected open
micro-pores; and e) the porous body comprises one or more open
cavities.
In one embodiment of the meniscus implant, the porous body is
C-shaped and comprises a plurality of cavities either regularly or
irregularly distributed over the porous body.
In another embodiment of the meniscus implant, the one or more
cavities may have a minimum diameter of about 1.5 mm, and
preferably about 2.0 mm.
In another embodiment of the meniscus implant, the one or more
cavities may have a maximum diameter of about 5.5 mm, and
preferably about 5.0 mm.
In again another embodiment of the meniscus implant, the cavities
penetrate through the porous body from an upper surface to a lower
surface.
In a further embodiment of the meniscus implant, the cavities are
cylindrical or prismatical and have a longitudinal axis each that
extends essentially orthogonally to the lower surface of the porous
body.
In a further embodiment of the meniscus implant, the cavities
penetrate into the porous body from the outer convex peripheral
surface in the form of pocket holes.
In again another embodiment of the meniscus implant, the porous
body further comprises transverse passages penetrating through the
porous body and through the cavities from the outer convex
peripheral surface to the inner concave peripheral surface.
In still another embodiment of the meniscus implant, the porous
body comprises interconnected pores that are open at the outer
convex peripheral surface, at the inner concave peripheral surface,
at the upper surface, and at the lower surface so as to promote
cellular in-growth.
In a further embodiment of the meniscus implant, the micro-pores
have a minimum diameter of about 120 .mu.m, and preferably about
150 .mu.m.
In again a further embodiment of the meniscus implant, the
micro-pores have a maximum diameter of about 370 .mu.m, and
preferably about 355 .mu.m.
In another embodiment of the meniscus implant, the porous body is
made of a material with an elastic modulus in tension E.sub.ci of
at least about 10 MPa measured in a circumferential direction, an
elastic modulus in tension E.sub.r of at least about 1 MPa measured
in a radial direction, and an elastic modulus in compression
E.sub.co of at least about 0.1 MPa. Typical ranges can be for the
elastic modulus in tension measured in a circumferential direction
E.sub.ci between about 10 MPa and about 300 MPa, the elastic
modulus in tension measured in a radial direction E.sub.r between
about 1 MPa and about 10 MPa and the elastic modulus in compression
E.sub.co between about 0.1 MPa and about 1.0 MPa.
In still another embodiment of the meniscus implant, the porous
body is made of a synthetic material, preferably of
polyurethane.
In yet another embodiment of the meniscus implant, the
interconnected pores of the porous body are filled with a
hydrogel-like substance containing cells.
For example and without limitation, the meniscus implant can be
used for replacement of a native meniscus.
In accordance with another aspect, a meniscus implant is provided
comprising a porous body with a central axis; the porous body
comprising:
I) an outer convex peripheral surface and an inner concave
peripheral surface;
II) an upper surface and a lower surface; and
III) a cross-sectional area orthogonal to the central axis and
tapering towards the inner concave peripheral surface, wherein
IV) the porous body comprises a number M of spikes protruding from
the outer convex peripheral surface of the porous body to permit
the meniscus implant to be attached to the native rim.
In another embodiment of the meniscus implant, the porous body
comprises cannulations penetrating through the spikes and into the
porous body towards the inner concave peripheral surface so as to
permit blood flow into the meniscus implant.
In a further embodiment of the meniscus implant, the cannulations
have a minimum diameter of about 0.4 mm, and preferably about 0.45
mm.
In again a further embodiment of the meniscus implant, the
cannulations have a maximum diameter of about 1.0 mm, and
preferably about 0.55 mm.
In another embodiment of the meniscus implant, the porous body
comprises micro-pores with a minimum diameter of about 120 .mu.m,
and preferably about 150 .mu.m.
In another embodiment of the meniscus implant, the porous body
comprises micro-pores with a maximum diameter of about 370 .mu.m,
and preferably about 355 .mu.m.
In yet another embodiment of the meniscus implant, the porous body
is made of a material with an elastic modulus in tension E.sub.ci
of at least about 10 MPa measured in a circumferential direction,
an elastic modulus in tension E.sub.r of at least about 1 MPa
measured in a radial direction and an elastic modulus in
compression E.sub.co of at least about 0.1 MPa. Typical ranges can
be for the elastic modulus in tension measured in a circumferential
direction E.sub.ci between about 10 MPa and about 300 MPa, the
elastic modulus in tension measured in a radial direction E.sub.r
between about 1 MPa and about 10 MPa and the elastic modulus in
compression E.sub.co between about 0.1 MPa and about 1.0 MPa.
In again another embodiment of the meniscus implant, the porous
body is made of a synthetic material, such as polyurethane.
In still another embodiment of the meniscus implant, the number M
of spikes is between about 1 and about 10.
In a further embodiment of the meniscus implant the interconnected
pores of the porous body are filled with a hydrogel-like substance
containing cells.
BRIEF DESCRIPTION OF THE DRAWINGS
Like reference numerals in the figures represent and refer to the
same or similar element or function. Implementations of the
inventive concepts disclosed herein may be better understood when
consideration is given to the following detailed description
thereof. Such description makes reference to the annexed pictorial
illustrations, schematics, graphs, drawings, and appendices. In the
drawings:
FIG. 1 is a top view of an exemplary embodiment of a meniscus
implant according to the inventive concepts disclosed herein shown
fixed to a rim of native meniscus material.
FIG. 2 is a sectional view taken along line 2-2 of FIG. 1.
FIG. 3 is a cut away view of a portion of a native meniscus and a
sectional view of a punching tool used in an embodiment of the
method according to the inventive concepts disclosed herein.
FIG. 4 is a top view of another embodiment of a meniscus implant
according to the inventive concepts disclosed herein shown fixed to
a rim of native meniscus material.
FIG. 5 is a sectional view taken along line 5-5 of FIG. 4.
FIG. 6 is a top view of another embodiment of a meniscus implant
according to the inventive concepts disclosed herein shown fixed to
a rim of native meniscus material.
FIG. 7 is a sectional view taken along line 7-7 of FIG. 6.
FIG. 8 is a top view of a tibial plateau with an exemplary
embodiment of a meniscus implant according to the inventive
concepts disclosed herein attached to the tibia in the area of the
posterior horn of the meniscus implant.
FIG. 9A illustrates a top view of an exemplary embodiment of a
meniscus implant according to the inventive concepts disclosed
herein with indication of the measuring direction of the elastic
moduli in tension.
FIG. 9B is a cross-sectional view taken along line 9B-9B of FIG. 9A
with indication of the measuring direction of the elastic modulus
in compression.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
Before explaining at least one embodiment of the inventive concepts
disclosed herein in detail, it is to be understood that the
inventive concepts are not limited in their application to the
details of construction and the arrangement of the components or
steps or methodologies set forth in the following description or
illustrated in the drawings. The inventive concepts disclosed
herein are capable of other embodiments or of being practiced or
carried out in various ways. Also, it is to be understood that the
phraseology and terminology employed herein is for the purpose of
description only and should not be regarded as limiting the
inventive concepts disclosed and claimed herein in any way.
In the following detailed description of embodiments of the
inventive concepts, numerous specific details are set forth in
order to provide a more thorough understanding of the inventive
concepts. However, it will be apparent to one of ordinary skill in
the art that the inventive concepts within the disclosure may be
practiced without these specific details. In other instances,
well-known features have not been described in detail to avoid
unnecessarily complicating the instant disclosure.
As used herein the notation "a-n" appended to a reference numeral
is intended as merely convenient shorthand to reference one, or
more than one, and up to infinity, of the element or feature
identified by the respective reference numeral (e.g., 134a-n).
Similarly, a letter following a reference numeral is intended to
reference an embodiment of the feature or element that may be
similar, but not necessarily identical, to a previously described
element or feature bearing the same reference numeral (e.g., 148,
148a, 148b, etc.). Such shorthand notations are used for purposes
of clarity and convenience only, and should not be construed to
limit the instant inventive concept(s) in any way, unless expressly
stated to the contrary.
Further, unless expressly stated to the contrary, "or" refers to an
inclusive "or" and not to an exclusive "or." For example, a
condition A or B is satisfied by anyone of the following: A is true
(or present) and B is false (or not present), A is false (or not
present) and B is true (or present), and both A and B are true (or
present).
In addition, use of the "a" or "an" are employed to describe
elements and components of the embodiments herein. This is done
merely for convenience and to give a general sense of the inventive
concepts. This description should be read to include one or at
least one and the singular also includes the plural unless it is
obvious that it is meant otherwise.
Finally, as used herein any reference to "one embodiment" or "an
embodiment" means that a particular element, feature, structure, or
characteristic described in connection with the embodiment is
included in at least one embodiment. The appearances of the phrase
"in one embodiment" in various places in the specification are not
necessarily all referring to the same embodiment.
Referring now to the drawings, and more particularly to FIGS. 1 and
2, a meniscus implant 100 for replacing damaged meniscal tissue is
illustrated attached to a rim 101 of native meniscus. The meniscus
implant 100 includes a porous body 102 with a first end 106 and a
second end 108. The first end 106 may be referred to as a posterior
horn, and the second end 108 may be referred to as anterior horn,
for example. The porous body 102 further has an outer convex
peripheral surface 110, an inner concave peripheral surface 112, an
upper surface 114, and a lower surface 116. As shown in FIG. 2, the
porous body 102 has a cross-sectional area in a plane orthogonal to
the lower surface 116 which tapers to the inner concave peripheral
surface 112.
The lower surface 116 of the porous body 102 may be planar. The
upper surface 114 can be a part of a conical surface or can be
concavely curved, for example. The outer convex peripheral surface
110 can be orthogonal to the lower surface 116 of the porous body
102. The upper surface 114 may taper such that the porous body 102
has a first height at the outer convex peripheral surface 110 and a
second height at the inner concave peripheral surface 112, each
measured orthogonally to the lower surface 116 of the porous body
102. The first height measured at the outer convex peripheral
surface 110 and/or the second height measured at the inner concave
peripheral surface 112 can be constant between the first end 106
and the second end 108. Alternatively, the first height of the
porous body 102 measured at the outer convex peripheral surface 110
and/or the second height measured at the inner concave peripheral
surface 112 of the porous body 102 can increase or decrease towards
the first end 106 and the second end 108 of the porous body
102.
The porous body 102 further comprises one or more interconnected
micro-pores 118 which are open at the outer convex peripheral
surface 110, at the inner concave peripheral surface 112, at the
upper surface 114, and at the lower surface 116. The interconnected
micro-pores 118 may have a diameter between about 120 .mu.m and
about 370 .mu.m, for example. The interconnected micro-pores 118 of
the porous body 102 may be filled with a hydrogel-like substance
containing cells (not shown).
The porous body 102 may be substantially C-shaped and may have a
plurality of open cavities 120 formed therein. FIG. 1 illustrates
the meniscus implant 100 as having nine open cavities 120, but it
will be appreciated that the number may be varied. The open
cavities 120 can be cylindrical or prismatical, and may have a
longitudinal axis 122 that extends essentially orthogonally to the
lower surface 116 of the porous body 102, so that the longitudinal
axes 122 of the open cavities 120 extend in the cranio-caudal
direction and in a plurality of sagittal planes. For example, as
illustrated in FIG. 1, the open cavities 120 can be arranged in
such a way that the longitudinal axis 122 of the open cavities 120
are equally spaced along the porous body 102. The open cavities 120
may each have a diameter between about 2.0 mm and about 5.0 mm.
Alternatively, the open cavities 120 can be distributed irregularly
over the porous body 102.
The porous body 102 may further comprise transverse passages 124
penetrating through the porous body 102 and through the open
cavities 120 from the outer convex peripheral surface 110 to the
inner concave peripheral surface 112. Each transverse passage 124
intersects one of the open cavities 120, preferably in the middle
of the height of the respective open cavity 120. Pieces of native
meniscus material 126 can be fixed within the open cavities 120 of
the porous body 102 by a press fit, and additionally by leading a
suture 128 through the transverse passages 124 and through the
pieces of native meniscus material 126 inserted in the open
cavities 120. The open cavities 120 can be regularly distributed
over the porous body 102.
The porous body 102 can be made of a synthetic material, e.g., a
polyurethane with an elastic modulus in tension measured in a
circumferential direction E.sub.ci between about 10 and about 300
MPa, an elastic modulus in tension measured in a radial direction
E.sub.r between about 1 and about 10 MPa, and an elastic modulus in
compression E.sub.co between about 0.1 and about 1.0 MPa (FIGS.
9A-9B).
Referring now to FIGS. 4-5, another embodiment of a meniscus
implant 100a may be substantially similar to the meniscus implant
100 of FIGS. 1 and 2, except the meniscus implant 100a includes a
porous body 102a with a plurality of cavities 120a arranged in such
a way that a longitudinal axis of the cavities 120a extend in a
transverse plane of the human body and that the porous body 102a
has no transverse passages. The open cavities 120a penetrate into
the porous body 102a from the outer convex peripheral surface 110a
in the form of pocket holes 130. Alternatively, the open cavities
120a can be staggered so that their longitudinal axes can extend,
e.g., alternatingly in two or more transverse planes. Pieces of
native meniscus material 126 can be fixed within the open cavities
120a of the porous body 102a by gluing a grid or a membrane 132 on
the outer convex peripheral surface 110a over each open cavity
120a. Alternatively, the pieces of native meniscus material 126 can
be glued directly into the open cavities 120a.
In another embodiment, the porous body 102a can comprise transverse
passages penetrating through the porous body 102a and through the
open cavities 120a from the outer convex peripheral surface 110a to
the inner concave peripheral surface 112a similarly to the
embodiment of FIGS. 1-2. Each transverse passage can intersect one
of the open cavities 120a, preferably in the middle of the height
or diameter of the respective open cavity 120a. Therefore, pieces
of native meniscus material 126 can be additionally fixed within
the open cavities 120a of the porous body 102a by a press fit and
by leading a suture through the transverse passages and through the
pieces of native meniscus material 126 inserted in the open
cavities 120a.
Another embodiment of a meniscus implant 134 is illustrated in
FIGS. 6-7. The meniscus implant 134 includes a porous body 136 with
an outer convex peripheral surface 140, an inner concave peripheral
surface 142, an upper surface 144, and a lower surface 146. In one
embodiment, the porous body 136 may be C-shaped, as shown. However,
the porous body 136 may be formed into any desired shape. The
porous body 136 has a cross-sectional area orthogonal to the lower
surface 146 which tapers towards the inner concave peripheral
surface 142. The lower surface 146 of the porous body 136 is
substantially planar.
The upper surface 144 can be a part of a conical surface or can be
concavely curved. The outer convex peripheral surface 140 can be
orthogonal to the lower surface 146 of the porous body 136. The
porous body 136 can have a height at the outer convex peripheral
surface 140 and a height at the inner concave peripheral surface
142 each measured orthogonally to the lower surface 146 of the
porous body 136. The height measured at the outer convex peripheral
surface 140 and/or the height measured at the inner concave
peripheral surface 142 can be constant between a first end 148 and
a second end 150. Alternatively, the height of the porous body 136
measured at the outer convex peripheral surface 140 and/or the
height measured at the inner concave peripheral surface 142 of the
porous body 136 can increase or decrease towards the first end 148
and second end 150 of the porous body 136.
Similar to the porous body 102 described above, the porous body 136
is shown to have a plurality of open cavities 152 in which pieces
of native meniscus material 126 may be fixed in a manner described
above. It will be understood that the open cavities 152 may also be
arranged in a manner similar to that shown in FIGS. 4-5 with
respect to the open cavities 120a.
The porous body 136 may comprise one or more open interconnected
micro-pores 154 which may have a diameter between about 120 .mu.m
and about 370 .mu.m. The interconnected micro-pores 154 of the
porous body 136 can be filled with a hydrogel-like substance
containing cells.
Furthermore, the porous body 136 has a plurality of spikes 156
protruding from the outer convex peripheral surface 140 of the
porous body 136 to facilitate attachment of the meniscus implant
134 to the native rim 158. The spikes 156 can have the shape of
truncated cones or truncated pyramids. The spikes 156 may be
arranged in such a way that their central axes extend in a
direction essentially parallel to the lower surface 146 of the
porous body 136 and extend from the outer convex peripheral surface
140 in a radial pattern when viewed from a top view. The spikes 156
can be regularly or irregularly distributed over the outer convex
peripheral surface 14 of the porous body 136. For example, the
spikes 156 may be located at a height measured from the lower
surface 152 of the porous body 136 which can be in range of about
35% to about 55% of the height of the outer convex peripheral
surface 146 of the porous body 136, for example.
The porous body 136 may further include cannulations 162 extending
through the spikes 156 to facilitate blood flow to the porous body
136. The cannulations 162 can have a diameter between about 0.4 mm
and about 1.0 mm, for example.
The porous body 136 can be made of a synthetic material, e.g., a
polyurethane with an elastic modulus in tension measured in a
circumferential direction E.sub.ci between about 10 to about 300
MPa, an elastic modulus in tension measured in a radial direction
E.sub.r between about 1 to about 10 MPa and an elastic modulus in
compression E.sub.co between about 0.1 and about 1.0 MPa (FIGS. 9A
and 9B).
A first embodiment of a method for replacing damaged meniscal
tissue can be performed by using the embodiment of the meniscus
implant 100 according to FIGS. 1-3. An incision permitting a
surgical access to at least one of the menisci in a knee joint may
be performed, and a portion 170 of a native meniscus 172 (FIG. 3)
may be cut away so that a rim 158 of native meniscus material at an
outer convex side 174 of the native meniscus 172 remains. Then, a
meniscus implant 100 of a desired size and having a desired number
N of open cavities 120 is selected.
As illustrated in FIG. 1, the meniscus implant 100 may comprise a
porous body 102 with exemplarily N=9 open cavities 120 with a
longitudinal axis 122 each. The meniscus implant 100 comprises open
cavities 120 penetrating through the porous body 102 from the upper
surface 114 to the lower surface 116 so that the open cavities 120
are arranged with their longitudinal axes 122 extending in a
cranio-caudal direction. Exemplarily, the open cavities 120 of the
porous body 102 are circular cylindrical and have a first diameter
d. Further, the porous body 102 can comprise transverse passages
124 penetrating through the porous body 102 and through the open
cavities 120 from the outer convex peripheral surface 110 to the
inner concave peripheral surface 112. If necessary the meniscus
implant 100 can be trimmed to a desired shape by using, e.g., a
chisel.
A number N of pieces of native meniscus material 126 may be punched
out of the native meniscus 172. The open cavities 120 of the porous
body 102 can then be filled with material gained from the
meniscectomy. The pieces of native meniscus material 126 are
preferably punched out of the cut away portion 170 of the patient's
native meniscus 172, e.g., by using a punching die 176 that has a
bore 178 with a second diameter D that is larger than the first
diameter d of the open cavities 120. Then, a piece of native
meniscus material 126 is inserted into each open cavity 120 in the
meniscus implant 100. Because the pieces of native meniscus
material 126 have a second diameter D which is larger than the
first diameter d of the open cavities 120, the pieces of native
meniscus material 126 are at least partially fixed in the open
cavities 120 by a press fit.
The pieces of native meniscus material 126 can be further fixed
within the open cavities 120 by leading a suture 128 through the
transverse passages 124 and through the pieces of native meniscus
material 126, preferably in the middle of the height of the pieces
of native meniscus material 126. The suture 128 can be successively
led through the transverse passages 124 and through the pieces of
native meniscus material 126 in a meander line and may be firmly
tightened with a knot at each end, or otherwise secured. The pieces
of native meniscus material 126 are then additionally fixed to the
porous body 102 by means of the suture 128 running through the
transverse passages 124 and penetrating the pieces of native
meniscus material 126 in the middle of their height, for example.
The material from the native meniscus 172 is so held in place not
only via this suture 128, but as well by the press fit, which is
obtained by using the punching die 176 with a larger inner diameter
than the diameter of the open cavity 120. This press fit may mimic
the existence of pre-stresses during in vivo remodeling.
Afterwards, the meniscus implant 100 including the pieces of native
meniscus material 126 may be inserted between a femoral condyle
(not shown) and the tibial plateau 180 in a patient's knee joint,
so that the outer convex peripheral surface 110 of the porous body
102 abuts the inner concave side 182 of the rim 158 of remaining
native meniscus 172 material. Then the meniscus implant 100 can be
fixed to the rim 140 of native meniscus 172 material with a
plurality of suture loops 184 wherein each suture loop 184 is led
through the porous body 102 and the rim 158 of native meniscus 172
material. Finally, the incision may be closed.
If the entire native meniscus 170, except the rim 158 has to be
removed, an additional fixation of the first end 106 and the second
end 108 of the meniscus implant 100 may be necessary. As
illustrated in FIG. 8, the fixation of the first end 106 of the
meniscus implant 100 to the tibia 188 can be effected via a bore
hole 190 that is drilled from the peripheral wall 192 of the tibia
188 and through the tibial plateau 180 at the former attachment
site of the posterior or anterior horn of the native meniscus 172.
The first end 106 of the meniscus implant 100 can then be affixed
to the tibia 188 by a thread 194 that is led through the bore hole
190 and anchored at the peripheral wall 192 of the tibia 188, e.g.,
by a knot. Alternatively, the fixation of the second end 108 and/or
first end 106 of the meniscus implant 100 can be realized with
plug-like fixation devices which are pressed into the tibial
plateau 180.
A second embodiment of the method for replacing damaged meniscal
tissue can be performed by using the embodiment of the meniscus
implant 100a according to FIGS. 4-5. This second embodiment of the
method differs from the first embodiment in that the meniscus
implant 100a according to the embodiment of FIGS. 4-5 is selected
and that the fixation of the pieces of native meniscus material 126
in the open cavities 120a is effected via a grid or membrane 132
which is fixed to the porous body 102a after insertion of the
pieces of native meniscus material 126 in the open cavities 120a.
The meniscus implant 100a illustrated in FIG. 4 exemplarily
comprises N=5 open cavities 120a that are arranged in such a way
that the longitudinal axes of the N=5 open cavities 120a extend in
a transverse plane of the human body. The open cavities 120a
penetrate into the porous body 102a from the outer convex
peripheral surface 110a so that a lateral opening 164 of each open
cavity 120a faces the rim 158 of the trimmed meniscus after
meniscectomy. The open cavities 120a are in the form of pocket
holes. The pieces of native meniscus material 126 can be fixed
within the open cavities 120a of the porous body 102a, e.g., by
gluing a grid or a membrane 132 on the outer convex peripheral
surface 110a over each open cavity 120a, or can be fixed within the
open cavities 120a by gluing only, for example. In an alternative
embodiment, the porous body 102a can comprise transverse passages
similar to transverse passages 124 of the porous body 102,
penetrating through the porous body 102a and through the open
cavities 120a from the outer convex peripheral surface 110a to the
inner concave peripheral surface 112a. The pieces of native
meniscus material 126 can be additionally fixed within the open
cavities 120a of the porous body 102a by a press fit and/or by
leading a suture through the transverse passages and through the
pieces of native meniscus material 126 inserted in the open
cavities 120a.
Similarly to the first embodiment of the method, an additional
fixation of the first end 106 and/or the second end 108 of the
meniscus implant 100a can be necessary if the entire native
meniscus except the rim 158 has to be removed as exemplarily
illustrated in FIG. 8 for a fixation of the first end 106a of the
meniscus implant 100a to the tibia 188.
FIGS. 9A-9B schematically illustrate the measuring directions of
the elastic moduli in tension E.sub.ci; E.sub.r and the elastic
modulus in compression E.sub.co. The following definitions apply
for the porous bodies 102 and 102a of the meniscus implants 100 and
100a according to each of the embodiments of FIGS. 1-5 as well as
for the porous body 136 of the meniscus implant 134 according to
FIGS. 6-7. E.sub.ci is the elastic modulus in tension measured in a
direction along the principal fiber, i.e., along the longitudinal
axis or in a circumferential direction of the porous body 102, the
porous body 102a, and the porous body 136. E.sub.r is the elastic
modulus in tension measured in a radial direction of the porous
body 102, the porous body 102a, and the porous body 136, i.e.,
transversely to the principal fiber or circumference and E.sub.co
is the elastic modulus in compression measured in a direction
orthogonal to the lower surface 116 of the porous body 102, the
lower surface 116a of the porous body 102a, or the lower surface
146 of the porous body 136.
From the above description, it is clear that the inventive concepts
disclosed herein are well adapted to carry out the objects and to
attain the advantages mentioned herein as well as those inherent in
the inventive concepts disclosed herein. While exemplary
embodiments of the inventive concepts disclosed herein have been
described for purposes of this disclosure, it will be understood
that numerous changes may be made which will readily suggest
themselves to those skilled in the art and which are accomplished
within the scope of the inventive concepts disclosed and as defined
in the appended claims.
* * * * *